This diagram shows electrons bumping into ions cause resistance. If the length of the wire is doubled, the electrons bump into twice as many ions so there will be twice as much resistance.
I’m going to summary my prediction to make it very clear. Longer the wire the more resistance the material has to electrical current compared to the short wire. This is so because the longer the wire, means more material and particles are included in the face of electrical current which has to struggle more to overcome these particles.
Variables
The key variables in my experiment include the three materials (Copper, Nichrome and Constantan, length of wire, and diameter (or thickness) of wire.
First I will investigate the effect of material on resistance by measuring the resistance of the three materials while keeping the length of wire (10cm) and diameter of the wire (30cm) the same. This will allow me to see which material offers the highest and lowest resistance. From my experiment set-up I shall read the voltage and current using the voltmeter and ammeter, respectively. From these readings I can calculate the respective resistance of each material. . In this experiment I will be observing and repeating this experiment 3 times to give a much more accurate set of results. Secondly I shall vary the length of the wire while keeping the diameter of wire (30 cm) and type of wire as fixed variables, in order to investigate the effect of wire length on the resistance. Again I shall measure the voltage and current using the voltmeter and ammeter, respectively to allow me to calculate the wire resistance at various wire lengths. The range of wire length I am going to investigate varies from 10 cm to 100 cm. This allows me to have a fair test on the effect of wire length on resistance. Also In this experiment I will be observing and repeating this experiment 3 times to give a much more accurate set of results. I will take the average of the three measurements for each material in order to get reliable results to calculate the resistance. Since there are three materials there will be nine measurements for voltage and current.
Fair Test
To make my experiment a fair test I will need to keep certain variables the same, and in this experiment, the effect of material on resistance, I will keep the following variables the same.
Constant variables
- Length of wire the same (10cm)
- The diameter of the wire (30cm)
- Temperature
- Current
The importance of keeping the variable the same is vital, because it might effect our results. Also I’m going to explain whys its important to keep this variables and explain how this would effect my set of results
Temperature
We must keep the surrounding room temperature the same or the particles in the wire will move faster (if the temperature is increased) and this will therefore have an effect on the resistance.
Length of wire the same
I must keep the length of the wire the same because As the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher, and effect our results
Material of wire
The material of the wire must also be kept the same as different materials have different conductivity and this will therefore have an effect on the resistance, which might effect our results.
Current
The current that we pass through the wire is to be kept the same, also. If this is changed the temperature of the wire might change in a way that is not constant making the results more difficult and confusing, which might affect my results
Experiment 2
In my second experiment, to make it a fair test, is by keeping the length of the wire the same. Also I’m going to explain whys its important to keep this variables and explain how this would effect my set of results.
Constant Variables
- Temperature
- The diameter the same
- Material of wire
- Current
Temperature
We must keep the surrounding room temperature the same or the particles in the wire will move faster (if the temperature is increased) and this will therefore have an effect on the resistance.
The Diameter The Same
We must keep the diameter the same because it will affect the resistance because the wider a wire the more space in the net for the charged electrons to get through without colliding with the net and therefore decreasing the resistance and effects our results.
Material of wire
The material of the wire must also be kept the same as different materials have different conductivity and this will therefore have an effect on the resistance, which might effect our results.
Current
The current that we pass through the wire is to be kept the same, also. If this is changed the temperature of the wire might change in a way that is not constant making the results more difficult and confusing, which might affect my results.
Method
Firstly, I will collect together the following equipment such as Ammeter, Batteries, Wires and voltage.
Next step is to connect all the equipment together to produce a circuit, like the one shown below.
Then I will record my readings on the different types of materials (Copper, Constantan and Nichrome) to see the effect of each type of material on the resistance.
I will then repeat each experiment 3 times. Finally when I have repeated the process three times, then soon I will want to compare it to see if it was equal to the first experiment. This is how I will collect my results; place different material in the circuit and the record the results (current and voltage). I will take 3 numbers of readings.
In the other Experiment – First thing that I’m going to do is to find a suitable metre ruler which match’s my requirements and then place a length of wire over a metre long and sellotaped it to a metre rule. Then I’m going clip a crocodile clip at the reading, which say 0cm. And then attached another crocodile clip which moves up and down the wire, stopping at 10,20,30,40,50, 60, 80, 90 and 100cm.In this experiment I’m going to read the voltage and the current from its ammeter and voltage meter very carefully, this is because it will allow me to calculate the resistance of each length, Each time reading the ammeter and voltmeter to work out resistance R = V/I.
Ranges of numbers and readings
The range of wire length I am going to investigate varies from 10 cm to 100 cm. This allows me to have a fair test on the effect of wire length on resistance. Also In this experiment I will be observing and repeating this experiment 3 times to give a much more accurate set of results. I will take the average of the three measurements for each material in order to get reliable results to calculate the resistance. Since there are three materials there will be nine measurements for voltage and current.
Accuracy
To keep this experiment as accurate as possible we need to make sure, firstly, that the length of the wire is measured precisely from the inside edge of the crocodile clips, making sure that the wire is straight when we do this. We must also make sure that the wire is straight when we conduct the experiment. If it is not, short circuits may occur and bends in the wire may effect the resistance, also. The reading that we take of the voltage should be done fairly promptly after the circuit is connected. This is because as soon as a current is put through the wire it will get hotter and we want to test it when heat is effecting it the least,
Analysis
The way I calculated the resistance on each materials (Copper, Constantan and Nichrome) and on the length of wire was by using Ohm’s law, which is given as:
Table 2: Resistance of three Materials at fixed length and diameter
First Try
Second Try
Third Try
Material Graph A
Table 3: Effect of wire Length on resistance at fixed diameter and material
First Try
Second Try
Third Try
Length of wire graph
Analysis continued
Graph A
I have noticed a pattern in graph A, The material that allows the most current in is copper then Constantan and the least is Nichrome. As the voltage decreased then the current increased. There is one prediction that I think, which is that copper does not hold the electron as tightly and the other material. Therefore my predictions was correct because as I changed the material (copper, constantan and Nichrome had different readings on the ammeter, this is because different materials hold there electron tightly or not tightly.
In my prediction early on I said that:
As I change the materials (Copper, Constantan and Nichrome) different readings from the ammeter and voltage will occur, and I expected that copper will have the least resistance of the three materials, followed by constantan, and then nichrome. In other words I expect copper to be the highest conducting material, and nichrome the lowest conducting material, while constantan ranks second to copper. The reason is that copper allows more current to flow because it does not hold the electrons very hard compared to constantan and nichrome which are alloys that hang on to their electrons more tightly and therefore tend to have high resistance to electrical current. The following electron distribution shapes give qualitative ideas as to why copper has highest conductivity (and least resistance), and nichrome the lowest conductivity (and highest resistance) of the three materials
Constantan
The reason why constantan does not allow current to pass throw is because constantan hold the electron very hard and makes it more difficult for the current to flow through the mental, also gives lots of energy is released.
Nichrome
The reason why Nichrome does not allow current to pass throw is because nichrome hold the electron very hard and makes it more difficult for the current to flow through the mental, also gives lots of energy is released.
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Copper
The reason why copper allow current to pass throw is because copper does not hold the electron very hard as nichrome and constantan and so is allows more current, and also releases energy.
Also I predict Copper allows more current because copper does not hold on to their electrons very hard as nichrome and constantan, which eventually allows more current to pass through, and also releases energy. We say copper is a good conductor of electricity or a low resistance to electricity. On the other hand constantan and nichrome have high resistance to electricity compared to copper. They are used to reduce the current in the circuit. Constantan is an alloy used for general purposes.; sometimes is called contra or eureka. Microbe is an alloy from which the elements of electric fires are made, since it resists oxidation when rod hot. The resistance of constantan is about twenty-five times that of copper, and nichrome about sixty times that of copper. Table 1 below give the values of conductivity for the three materials. The conductivity is the inverse of resistively.
Table 1: conductivity of some materials
So overall I do agree with my original prediction ,which I made early on
Graph B
I have noticed a pattern in graph B, as the length of the wire increases the resistance increased as well. This shows that the length of the wire affects the resistance. Suppose, for instances, that the length of a given wire is doubled. This doubles the resistance, since twice the length of wire is equivalent to two equal resistances in series. If the length of wire is increased five times the resistance likewise becomes five times its previous value, and so on. This is because as we increase the length of the length of the material, so does the resistance because increasing the mass or the number of protons inside the wire, so It has to overcome the larger number of particles of the wires, therefore, the resistance of the wire increases.
Early on in my prediction I stated that:
The longer the wire the more resistance the material has to electrical current compared to the short wire. This is so because the longer the wire, means more material and particles are included in the face of electrical current which has to struggle more to overcome these particles.
Also as the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher. Resistance, in ohms (R) is also equal to the resistively of the wire.
Also in my prediction I stated that I believe that the rate at which the resistance of the wire increases will be directly proportional to the length, this is because structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current
Electric current is the movement of electrons through a conductor. In this experiment a metal wire (Copper, Constantan and Nichrome will be the conductor). So when resistance is high, conductivity is low. Metals such as Copper, Constantan and Nichrome conduct electricity well because the atoms in them do not hold on to their electrons very well. Free electrons are created, which carry a negative charge, to jumps along the lines of atoms in a wire, which are in a lattice structure. Resistance is when these electrons, which flow towards the positive, collide with other atoms; they transfer some of their kinetic energy. This transfer on collision is what causes resistance. So, if we double the length of a wire, the number of atoms in the wire doubles. This increases the number of collisions and energy transferred twice, so twice the amount of energy is required. This means the resistance is doubled.
Also I stated that In circuits containing metallic conductors, the only particles that are free to move are electrons. Metals contain positive ions, neutral atoms that have lost one or two of their outermost electrons. Theses electrons are free to move about in the mental and are affected by electric forces. Any movement of charges is an electric current.
I think that from my results I can safely say that my prediction was right. The resistance did change in proportion to the length. This is because as the length of the wire increased the electrons that made up the current, had to travel through more of the fixed particles in the wire causing more collisions and therefore a higher resistance. We can work out what the resistively of the wire should be from our results using the formula.
Evaluation
I completed my experiment successfully because I have good results. My aim was to find out which material affected the resistance the most. I did find what I was looking for, which was that copper allows the most current through .I could have made my results more reliable by repeating it or checking it two times. I think that I did have enough measurement because I repeated my experiment 3 times and I also covered ever angle in my investigation .I think that I should not have taken an wider results because I have recorded all my results. I could have made my results more accurate by getting the same person to read the ammeter and the voltage. I could have not made my method more accurate because, I planned everything ahead .The equipment that I used to measure the current was a ammeter and for the push of the current I used an voltmeter. My repeated results were similar to my original ones. I did count the amount of current that flows through the materials. There was not one result that did not fit my pattern. All my results where as I expected to be for e.g. I expected copper to allow more current to flow in because it was not holding its electrons tightly. If I were to do my experiment again, I would try to improve it by collecting more research and to improve my concentration on that topic. If I were to do a different experiment on the same topic, I would do the length of wire that which the resistance. The other experiment that I could have done was the length of wire, which affected the resistance the most. The other variable that I could have tested if I was to do another experiment on the same topic where the measurement of the diameter of the wire e.g. 30cm, 32cm, 38cm I could have tested. Also the other variables that I could have tested were the length of the wire for e.g. 10 cm, 20cm, 30cm, 40cm and so on. In the Analysis and the graph I have shown one main anomalous point, this means that there must have been a slight error in my experiment. As the wire, length is bigger at these points I found it harder to stretch it out and consequently, measure it accurately. Although the graph is overall accurate and the results precise it is easy to see, the anomalous averages plotted because they do not all lie along the same best-fit line. The graph shows that my results are reliable as there are only one main anomalous points, (which are easily accounted for) to improve the reliability of my results, I could do more repeats in doing this my average would be more reliable. As I increased the wire length, the wire became hotter and gave off heat. This could explain why the anomalous results are at the top of my graph, 90cm
I have noticed several modifications I could make to improve on the Investigation if I was to repeat it.
The first of these modifications would be the circuit that I would use. To be more accurate with my results I would place the Metre rule directly under the wire, so therefore it would be measured easier and therefore making the lengths more precise.
Instead of connecting the voltmeter to the main circuit, I would connect it to the wire that is being tested. I would do this so that the voltmeter is measuring the voltage of just the wire being tested and not the wires of the main circuit as well.
To also improve on my results I could use a new or higher quality digital voltmeter. The next modification I would make would be to use pointers instead of crocodile clips to attach to the wire; I would do this because pointers would be more accurate. The pointers would be more accurate because the tips have a much smaller area than the crocodile clips giving a more accurate measurement of the length of wire. I would also use a newer metre rule. The graph shows that my results are reliable as there are only two anomalous points, to improve the reliability of my results, I could also have repeated the same lengths of wire more times
